The present invention relates to the field of digital communications. In particular, the present invention relates to an optimal method for provisioning a high-speed data connection between a user and a destination over a connection-oriented packet network having digital subscriber line access to the user premises.
With the explosive growth of the Internet and with the increasing desirability of telecommuting, the need for more reliable and higher speed data access over the xe2x80x9clast milexe2x80x9d to homes and small businesses has become apparent. In particular, it has become desirable to provide high-speed data communications (1) between remote users, such as users at homes or small businesses, and corporate networks for telecommuting purposes, and (2) between remote users and the Internet. A traditional method of remote user access, and still the most common, involves the use of two-wire modems, such as V.90 modems, to establish a dial-up connection between the remote user and their company""s dial-in server, or between the remote user and their Internet Service Provider (ISP). Although still having certain cost advantages, the traditional dial-up modem has many practical disadvantages including dial-up delay and including a limited data access rate, which is currently 56 Kbps for V.90 modems.
FIG. 1 shows a block diagram of an emerging technology and service solution that provides numerous advantages over traditional remote access methods. FIG. 1 shows a connection-oriented packet network 100 for providing a connection between a remote user and a destination where a DSL (Digital Subscriber Line) link is used to access the remote user premises. As used herein, xe2x80x9cremote userxe2x80x9d indicates a customer at a home, small business, or other location whose primary method of data connection to the outside world is through ordinary telephone system xe2x80x9clast milexe2x80x9d copper connections to the telephone company central office (CO).
As known in the art, connection-oriented protocols rely on end-to-end connections through virtual circuits. The virtual circuits are either Permanent Virtual Circuits (PVC""s) that are permanently xe2x80x9cnailed upxe2x80x9d, or Switched Virtual Circuits (SVC""s) that are established on a per-call basis. In a connection-oriented protocol, successive packets travel from the source to the destination over the same path, whereas for connectionless protocols each individual packet finds its own way through the network to its destination. Examples of connection-oriented protocols include Asynchronous Transfer Mode (ATM), Frame Relay, and X.25 Virtual Circuit Mode. Examples of connectionless protocols include the Internet Protocol (IP), X.25 Datagram Mode, and SMDS (Switched Multimegabit Data Service).
From a connectivity and throughput perspective relevant to the remote access network of FIG. 1, the newer connection-oriented protocols such as Frame Relay and ATM are advantageous for reasons including (a) higher data rates over the newer and more reliable hardware that is now available, as compared to connectionless lower-level protocols, and (b) the opportunity to define specific grades of service, such as CIR (Committed Information Rate) for Frame Relay and QoS (Quality of Service) metrics for ATM. See generally McDysan and Spohn, ATM: Theory and Application, Signature Edition, McGraw-Hill Series on Computer Communications (1998), the contents of which are hereby incorporated by reference into the present disclosure.
As known in the art, DSL technology affords the opportunity to establish high bit rate access over ordinary copper lines between remote user premises and the telephone company CO. DSL technology has been described as creating high-speed xe2x80x9cdumb pipesxe2x80x9d over ordinary copper lines, allowing high bandwidth to remote users at reduced cost. See K. Taylor, xe2x80x9cConverting Copper: How xDSL Paves the Way for ATMxe2x80x9d, in Gadecki and Heckart, ATM . . . , IDG Books Worldwide (1997) at pp. 91-93. The contents of the Gadecki and Keckart text are are hereby incorporated by reference into the present disclosure.
DSL technology, often named xDSL technology, comes in several different variations. High Bit Rate DSL (HDSL) is the oldest DSL technology, which arose from problems in transmitting T1 (1.544 Mbps) over long copper loops, offers symmetric (same speed both ways) data rates up to 1.544 Mbps in a 4-wire implementation, and up to 768 Kbps in 2-wire implementations. Symmetric DSL (SDSL) offers, in a single 2-wire implementation, a symmetric data rate of up to 1.1 Mbps and even 1.544 Mbps in light of recent improvements. Asymmetric DSL (ADSL) offers, in a single 2-wire implementation, the combination of a high-speed downstream channel that can deliver a one-way downstream rate of 1.5-8 Mbps to the remote user, along with a duplex channel that can deliver a symmetric data rate of up to 640 Kbps. Other types of DSL services have emerged including Rate Adaptive DSL (RADSL), ISDN DSL (IDSL), and Very High-Speed DSL (VDSL). See generally Chen, DSL: Simulation Techniques and Standards Development for Digital Subscriber Line Systems, MacMillan Technology Series (1998), the contents of which are hereby incorporated by reference into the present disclosure.
As shown in FIG. 1, the connection-oriented packet network 100 provides connectivity between a remote user or client premise 102, such as a home or small business, and a corporate LAN 104. Alternatively, or in conjunction therewith, the connection-oriented packet network 100 provides connectivity between the client premise 102 and the Internet 106 via ISP 108. As used herein, for simplicity and clarity of disclosure, the remote user is denoted as the xe2x80x9cclientxe2x80x9d of the remote data access service. It is to be appreciated that the xe2x80x9ccustomerxe2x80x9d of the remote data access service of FIG. 1, i.e. the party that requests the service and pays the service invoices, may actually be the client, the client""s employer, the ISP, or a different party depending on bundling, reselling, or other business and marketing factors. Unless otherwise indicated herein, and for purposes of clarity of disclosure and not by way of limitation, the xe2x80x9cclientxe2x80x9d shall correspond to a single entity at the remote user premise who requests, uses, and pays the remote data access service of FIG. 1.
In the case of the corporate LAN 104 as the destination, the connection-oriented packet network 100 provides a permanent virtual circuit (PVC) between the client premise 102 and the corporate LAN 104. Physically, (1) a DSL link 110 is provided between the client premise 102 to the CO 112, (2) a standard Time Division Multiplexed (TDM) link 114 (e.g., DS-3 or STS-3c) is provided between the CO 112 to an ATM network switch 116 of an ATM Network 118, (3) facilities of ATM Network 118 are provided between ATM network switch 116 and an ATM network switch 120 near the corporate LAN 104, and (4) a standard TDM link 122 (e.g., DS-1 or DS-3) is provided between ATM network switch 120 and the corporate LAN 104. The DSL link 110 is provisioned between (a) a remote DSL terminal unit 132 such as a DSL modem at the client premise 102, and (b) a CO DSL terminal unit 134 such as a DSL Access Multiplexer at the CO 112. The TDM link 122 between ATM network switch 120 and the corporate LAN 104 terminates at a router 107 at the corporate site.
Using the above facilities, in FIG. 1 an ATM circuit is provisioned between remote DSL terminal unit 132 and router 107, traversing the DSL link 110, the CO DSL terminal unit 134, the TDM link 114, the ATM switch 116, the ATM Network 118, the ATM switch 120, and the TDM link 122. For purposes of disclosing features and advantages of the preferred embodiments infra, the portion of the ATM circuit between the remote DSL terminal unit 132 and the CO DSL terminal unit 134 may be referred to as a digital subscriber line portion, while the portion of the ATM circuit between the CO DSL terminal unit 134 and the router 107 may be referred to as a connection oriented packet network portion.
In the case of the ISP 108 as the destination, the connection-oriented packet network 100 provides a similar PVC except that connectivity is provided between the ATM network switch 116 and a different ATM network switch 124 closer to the ISP 108 over a TDM link 126 to ISP 108. The TDM link 126 terminates at a router (not shown) at ISP 108 which provides connectivity to the Internet 106. Thus, in this case, an ATM circuit is provisioned between remote DSL terminal unit 132 and a router at ISP 108, traversing the DSL link 110, the CO DSL terminal unit 134, the TDM link 114, the ATM switch 116, the ATM Network 118, the ATM switch 124, and the TDM link 126.
It is to be appreciated, of course, that the router 107 at the interface to the corporate network, as well as the router (not shown) at the interface to ISP 108, represent endpoints of the connection-oriented packet network 100. The Internet 106 and LAN 104 are not in themselves part of the connection-oriented packet network 100. It is to be further appreciated that the ATM Network 118 is exemplary of a network that provides PVC and SVC services, but may contain, in whole or in part, portions that use a different connection-oriented protocol such as Frame Relay without departing from the scope of the preferred embodiments.
The connection-oriented packet network 100 of FIG. 1 is similar to a currently available service named TeleSpeed(copyright) offered by Covad Communications, the assignee of the present invention. As described on the Covad web site www.covad.com, the entirety of which is hereby incorporated by reference into the present disclosure as of the filing date, exemplary TeleSpeed(copyright) subscription services include: TeleSpeed(copyright) 144, which uses an IDSL connection between the customer premise and the CO that allows a symmetric 144 Kbps data rate, TeleSpeed(copyright) 192, which uses an SDSL connection between the customer premise and the CO that allows a symmetric 192 Kbps data rate; TeleSpeed(copyright) 384, which uses an SDSL connection for a symmetric 384 Kbps data rate; TeleSpeed(copyright) 768, which uses an SDSL connection for a symmetric 768 Kbps data rate; TeleSpeed(copyright) 1.1, which uses an SDSL connection for a symmetric 1.1 Mbps data rate; and TeleSpeede(copyright) 1.5, which uses an ADSL connection for offering of a downstream channel of up to 1.5 Mbps in combination with an upstream channel of up to 384 Kbps. It is to be appreciated, however, that the scope of the preferred embodiments is not limited to such implementations. For purposes of the present disclosure, the providers of high speed remote access using digital subscriber lines through connection-oriented packet networks, such as Covad Communications, may generically be referred to as end-to-end service providers.
As shown in FIG. 1, the client premise 102 usually contains one or more client computers, two such client computers 128 and 130 being shown in FIG. 1. Client computers 128 and 130 are each equipped with LAN access equipment such as 10BaseT Ethernet cards (not shown) for coupling to a client LAN 113. Any of a variety of protocols may be used for establishing data communications among client computers 110 and 112 over client LAN 113, including standardized protocols such as TCP/IP over Ethernet, proprietary protocols such as Novell IPX, or other protocols.
Connection-oriented packet network 100 comprises a DSL link 110 between a remote DSL terminal unit 132 and a CO DSL terminal unit 134. Remote DSL terminal unit 132 is coupled to the user LAN 113. The type of DSL terminal units 132 and 134 that are used will depend on the subscribed service and the type of equipment on the user LAN 113. For example, in the case of TeleSpeed(copyright) 144 service from Covad Communications, remote DSL terminal unit 132 may be an Ascend Pipeline 50/75, a Cisco 700 series router, a Cisco 1604 router, or a Flowpoint 144 router, while the CO DSL terminal unit 134 may be a Cisco 90i IDSL Channel Unit. In the case of TeleSpeed(copyright) 192, 384, 768, or 1.1 service from Covad Communications, remote DSL terminal unit 132 may be a FlowPoint 2200 SDSL router. In the case of TeleSpeed(copyright) 1.5 service from Covad Communications, remote DSL terminal unit 132 may be a Flowpoint 2100 ADSL router. CO DSL terminal unit 134 may be a Diamond Lane DSL Access Multiplexer. It is to be appreciated, of course, that the above exemplary equipment is listed for completeness of disclosure and so as not to cloud the features and advantages of the preferred embodiments. As line speeds increase and/or other technological advances are made, the implementations may use different equipment without departing from the scope of the preferred embodiments.
It is also to be appreciated that remote user premise 102 is one of tens, hundreds, or even thousands of client premises that may be connected over DSL lines similar to DSL line 110 for termination at the telephone company CO 112. Accordingly, the CO DSL terminal unit 134 may be one of many such units at the CO 112, and each CO DSL terminal unit may be coupled to several DSL lines depending on its capabilities. For simplicity and clarity of disclosure, however, only one such DSL line 110, remote DSL terminal unit 132, and CO DSL terminal unit is shown in FIG. 1.
At the telephone company CO 112, the network sides of the multiple DSL lines are multiplexed onto a high-capacity transmission line using, for example, a DSL Access Multiplexer for providing an ATM protocol connection between the DSL lines and the ATM network switch 116. The ATM network switch 116 may be, for example, a Cisco BPX(copyright) ATM switch. Between the ATM network and the corporate LAN 104 or ISP 108, data packets are delivered in accordance with the appropriate protocols, the details of which are beyond the scope of the present disclosure but which are described, at least in part, in the McDysan and Spohn text supra.
Provisioning refers to the process of configuring hardware and software to establish a virtual circuit between the client premise and the destination. Provisioning includes the process of establishing the DSL link 110 between the client premise 102 and the CO 112, as well as the process of establishing a virtual circuit between the CO 112 and the destination. In the case of permanent or xe2x80x9cnailed upxe2x80x9d data connections, as is the case with the exemplary TeleSpeed(copyright) services described supra, the service remains in its provisioned configuration unless changes occur. Such changes include, but are not limited to, interruptions in the ATM network such as link outages, interruptions in the DSL line such as the inadvertent unplugging of the client DSL unit, and maintenance interruptions in either portion. Upon such occurrences, the ATM network is designed to automatically reroute traffic and/or reestablish PVC connections, and the DSL units are designed to automatically re-train to establish DSL connectivity as soon as possible.
A problem occurs in the remote user data access network of FIG. 1 due to present-day provisioning processes. In particular, in prior art provisioning processes the DSL terminal units are configured to train at the highest obtainable speed, independent of the rate that is subscribed to by the customer. Often, the actual trained data rate between the DSL terminal units is much higher than the subscribed rate, simply because the facilities between the customer premise and the CO allow this higher trained rate to happen. As an example, it has been observed in some circumstances that the DSL terminal units will train as high as several megabits per second (Mbps), even though the subscribed rate was only 384 Kbps. However, the ATM network has only provisioned 384 Kbps for that remote user""s PVC. In this case, unwanted congestion can occur between the CO DSL terminal unit and the ATM network switch during bursts of data greater than the subscribed rate of 384 Kbps.
As described in ATM: Theory and Application, supra, at Chapter 23, the ATM protocol is designed to respond to the unwanted congestion through various means, which may include the invocation of Selective Cell Discard, i.e. the xe2x80x9cbit-bucketingxe2x80x9d of lower priority cells. Although higher-level protocols will ensure overall data integrity, e.g. by requesting re-send of the data by the client and/or destination computers, the overall efficiency of the end-to-end network is compromised, and a lower overall throughput may result.
FIG. 2 shows a diagram of a training sequence between DSL terminal units that causes the above congestion problem in prior art implementations of remote user access over DSL through connection-oriented packet networks. FIG. 2 shows a generic user DSL Modem 232 located at the remote user premises coupled to a generic DSL Access Multiplexer 234 located at the CO. In the example of FIG. 2, an SDSL symmetric connection of 384 Kbps is provisioned. In accordance with the prior art, the exemplary DSL Access Multiplexer 234 is capable of training to speeds 300, 400, 500, 600, 700, and so on, up to a maximum of several Mbps. The speeds 300, 400, 500, etc. represent the speed increments at which the DSL Access Multiplexer 234 can train. Due to hardware considerations, typical DSL Access Multiplexers 234 are incapable of training at speeds that lie between these speed increments. The user DSL Modem 232 is programmed to attempt to train at whatever speed attempted by the DSL Access Multiplexer 234. It is to be appreciated that the specific numbers 300, 400, 500, etc. used in this example were selected for clarity of disclosure, and are not intended to precisely represent the actual training speed steps of the existing physical devices. Actual training speeds of the existing physical devices vary depending on brand and other factors, but will generally vary in a manner analogous to this example.
In accordance with this prior art example, when the SDSL connection is first established, the DSL Access Multiplexer 234 will first attempt to train with the user DSL Modem 232 at the lowest data rate, that is, 300 Kbps. If copper facility conditions and loop length allow successful training with user DSL Modem 232 at 300 Kbps, then DSL Access Multiplexer 234 will increase the attempted training rate to the next speed increment, 400 Kbps. If successful, i.e. if copper facility conditions and loop length allow training with user DSL Modem 232 at 400 Kbps, then DSL Access Multiplexer 234 will increase the attempted training rate to the next level, 500 Kbps, and so on until the increase in attempted training speed causes training failure. Such a failure level is shown as 700 Kbps in FIG. 2. In this case, the DSL Access Multiplexer 234 and the DSL Modem 232 xe2x80x9csettlexe2x80x9d on a training rate of 600 Kbps.
Disadvantageously, in this prior art example where the DSL terminal units have trained at 600 Kbps, which is substantially higher than the subscribed rate of 384 Kbps, problems can occur. In particular, if the client transmits a substantially long burst of data at, say, 550 Kbps, then the ATM network will respond with congestion recovery measures, because it has only provisioned 384 Kbps for that PVC. These congestion recovery measures can include the xe2x80x9cbit bucketingxe2x80x9d described above, which results in retransmission requests from the higher order protocols and reduced end-to-end efficiency of the network.
Accordingly, it would be desirable to provision data access over DSL through connection-oriented packet networks, such that network congestion due to data rate mismatches between the DSL connection and the provisioned PVC channel is minimized.
It would further be desirable to provision data access over DSL through connection-oriented packet networks, such that enhanced services may be offered to the remote user in the event that the DSL connection is capable of training at a data rate substantially greater than the subscribed rate, based upon automatically learned knowledge of the difference between the maximum actual trainable DSL rate and the subscribed rate.
It would be even further desirable to provision data access over DSL through connection-oriented packet networks, such that resources in the connection-oriented packet network may be more efficiently utilized in the event that the actual trained DSL rate is substantially less than the subscribed rate provisioned rate.
It would be even further desirable to provision data access over DSL through connection-oriented packet networks, such that differences in available speed increments between the DSL link and the provisioned PVC channel are accommodated in a manner that does not xe2x80x9cpunishxe2x80x9d the remote user by excessively discarding cells during periodic bursts of data at speeds lying between respective speed increments.
In accordance with a preferred embodiment, a method and system for provisioning remote user data access over DSL through connection-oriented packet networks is provided, wherein the DSL terminal units associated with the DSL link are directed to train at a rate that is not substantially greater than a subscribed data rate. In this manner, network congestion due to data rate mismatches between the DSL connection and the corresponding PVC channel through the connection-oriented packet network is minimized or avoided.
According to another preferred embodiment, a provisioning process is provided wherein the DSL terminal units are directed to test for the maximum trainable data rate before settling to a trained data rate not substantially greater than the subscribed data rate, and to communicate the maximum trainable data rate to a network operations center computer. In this manner, the maximum allowable DSL data rate to each specific client premise is known by the network operations center, and can advantageously be used by the end-to-end service provider. For example, the maximum allowable DSL data rate may be compared to the client""s subscribed data rate and to the client""s actual traffic usage patterns, permitting enhanced services to be offered to the client by marketing personnel when appropriate. As another example, knowledge of the maximum allowable DSL data rates for a plurality of client premises may be used for facility routing and community data planning applications, and may be sold to digital content providers as valuable marketing data.
According to another preferred embodiment, in the event that the maximum trainable rate between DSL terminal units lies substantially below the subscribed data rate, the network operations center causes the automatic re-provisioning of the permanent virtual circuit (PVC) channel through the connection-oriented packet network such that the resulting PVC has a corresponding data rate lower than the subscribed data rate. In this manner, bandwidth that would otherwise go unused is released for allocation to other ATM channels, thereby conserving network resources and enhancing network efficiency.